Multicenter Study of Planar Technetium 99m Pyrophosphate Cardiac Imaging: Predicting Survival for Patients With ATTR Cardiac Amyloidosis

How to Image Cardiac Amyloidosis: A Practical Approach

Cardiac amyloidosis (CA) is one of the most rapidly progressive forms of heart disease, with a median survival from diagnosis, if untreated, ranging from <6 months for light chain amyloidosis to 3 to 5 years for transthyretin amyloidosis. Early diagnosis and accurate typing of CA are necessary for optimal management of these patients. Emerging novel disease modifying therapies increase the urgency to diagnose CA at an early stage and identify patients who may benefit from these life-saving therapies. The goal of this review is to provide a practical approach to echocardiography, cardiac magnetic resonance, and radionuclide imaging in patients with known or suspected CA.

A case report of an uncommon presentation of 99mtechnetium pyrophosphate scintigraphy in transthyretin cardiac amyloidosis: A potential diagnostic pitfall, pseudo-positive or pseudo-negative?

^99mTechnetium pyrophosphate (^99mTc-PYP) scintigraphy has shown utility for diagnosis of transthyretin (ATTR) cardiac amyloidosis with a high sensitivity and specificity. However, in clinical practice, a protocol and a method of analysis of this modality are not yet unified. We present a case of ATTR cardiac amyloidosis showing a positive cardiac uptake in planar imaging but no myocardial uptake in single-photon emission computed tomography/computed tomography (SPECT/CT) fusion imaging on ^99mTc-PYP scintigraphy. We considered this tracer accumulation in the cardiac blood pool to be an inconclusive study. In this report, we focus on an inconclusive study case as a potential pitfall of ^99mTc-PYP scintigraphy and discuss the interpretation of ^99mTc-PYP scintigraphy findings with using both planar and SPECT/CT imaging for improvement of diagnostic accuracy for ATTR cardiac amyloidosis. <Learning objective: The present report describes the importance of distinguishing myocardial uptake from the cardiac blood pool by both planar and single-photon emission computed tomography/computed tomography fusion imaging on ^99mtechnetium pyrophosphate (^99mTc-PYP) scintigraphy for diagnosis of transthyretin cardiac amyloidosis. To improve diagnostic accuracy, the ^99mTc-PYP scintigraphy protocol including the method of evaluation and interpretation of the findings should be unified.>.

Non-cardiac uptake of technetium-99m pyrophosphate in transthyretin cardiac amyloidosis

BACKGROUND

Technetium-based bone scintigraphy is rapidly becoming the most common non-invasive imaging tool in the diagnosis of Transthyretin cardiac amyloidosis (ATTR). Skeletal muscle uptake has been described with technetium-99m-3,3-diphosphono-1,2-propanodicarboxylic acid (TcDPD), and may account for masking of bony uptake. We sought to investigate skeletal muscle uptake of technetium-99m-pyrophosphate (TcPYP) in patients with ATTR.

METHODS AND RESULTS

This was a retrospective analysis of 57 patients diagnosed with ATTR who underwent TcPYP scintigraphy. Cardiac uptake was assessed on whole-body planar imaging using a semiquantitative scale (grades 0 to 3) and on single-photon emission computed tomography (SPECT) with CT attenuation correction using total myocardial counts per voxel after a 3-hour incubation. Skeletal muscle (psoas and biceps), vertebral body, LV myocardium, and blood pool mean counts were calculated. In the cohort (age 78 ± 9 years, 77% male, and 30% hereditary ATTR), there was no visualized tracer uptake in skeletal muscle or soft tissue on qualitative SPECT assessment. Total and blood pool-corrected uptake in the muscle groups were significantly less than myocardium and bone (P < 0.001). Blood pool-corrected muscle uptake was not associated with semiquantitative grade 3 vs 2 uptake (psoas P = 0.66, biceps P = 0.13) or presence of hereditary ATTR (psoas P = 0.43, biceps P = 0.69). As bony uptake decreased, there was no corresponding increase in skeletal muscle uptake.

CONCLUSIONS

In patients with ATTR cardiac amyloidosis, skeletal muscle uptake of TcPYP is minimal when assessed by qualitative and quantitative metrics, and is not significantly different in patients with grade 2 vs 3 semiquantitative uptake. The properties of this tracer may be different than TcDPD with respect to non-cardiac uptake.

Analogies and disparities among scintigraphic bone tracers in the diagnosis of cardiac and non-cardiac ATTR amyloidosis

In this issue of JNC, BW Spery and Coll report a retrospective analysis of 57 patients with transthyretin-related amyloidosis (ATTR) in an advanced phase of the disease who underwent 99mTechnetium-pyrophosphate (99mTcPYP) scintigraphy. Although relatively small and "negative," the study is relevant since it broadens our knowledge on the uptake of "bone tracers" in ATTR and contributes to understand the limitations of the clinical use of scintigraphy in this disease. The paper raises, directly or indirectly, at least three questions: To what extent are the different bone tracers interchangeable for the diagnosis of ATTR cardiac amyloidosis? Are bone tracers able to image non-cardiac ATTR amyloidosis? What is the explanation for the variable performance of the different bone tracers in the diagnosis of cardiac and extracardiac ATTR amyloidosis?

Transthyretin cardiac amyloidosis: an update on diagnosis and treatment

Transthyretin cardiac amyloidosis (ATTR‐CA) demonstrates progressive, potentially fatal, and infiltrative cardiomyopathy caused by extracellular deposition of transthyretin‐derived insoluble amyloid fibrils in the myocardium. Two distinct types of transthyretin (wild type or variant) become unstable, and misfolding forms aggregate, resulting in amyloid fibrils. ATTR‐CA, which has previously been underrecognized and considered to be rare, has been increasingly recognized as a cause of heart failure with preserved ejection fraction among elderly persons. With the advanced technology, the diagnostic tools have been improving for cardiac amyloidosis. Recently, the efficacy of several disease‐modifying agents focusing on the amyloidogenic process has been demonstrated. ATTR‐CA has been changing from incurable to treatable. Nevertheless, there are still no prognostic improvements due to diagnostic delay or misdiagnosis because of phenotypic heterogeneity and co‐morbidities. Thus, it is crucial for clinicians to be aware of this clinical entity for early diagnosis and proper treatment. In this mini‐review, we focus on recent advances in diagnosis and treatment of ATTR‐CA.

Amyloidosis cardiomyopathy: update in the diagnosis and treatment of the most common types

PURPOSE OF REVIEW

The present article provides an update about the recent advances in the diagnosis and management of the most common types of cardiac amyloidosis, including light chain, wild-type transthyretin (ATTRwt), and mutant transthyretin (ATTRm).

RECENT FINDINGS

The document reviews the utility of diagnostic tools including innovative echocardiographic indices, magnetic resonance T1 mapping and measurement of extracellular volume, and the role and validation of bone scintigraphy for the noninvasive assessment of ATTR amyloidosis. It summarizes the data about therapies for light chain amyloidosis including bortezomib regimens and also novel disease modifying therapies for ATTR amyloidosis such as gene silencers, transthyretin stabilizers, and degraders of amyloid fibrils.

SUMMARY

The present review provides the readers with the necessary tools in order to recognize and diagnose cardiac amyloidosis early and introduces the recent advances in management that are improving the outcomes of a condition that was considered to be untreatable.

Expert Consensus Recommendations for the Suspicion and Diagnosis of Transthyretin Cardiac Amyloidosis

Cardiomyopathy is a manifestation of transthyretin amyloidosis (ATTR), which is an underrecognized systemic disease whereby the transthyretin protein misfolds to form fibrils that deposit in various tissues and organs. ATTR amyloidosis is debilitating and associated with poor life expectancy, especially in those with cardiac dysfunction, but a variety of treatment options have recently become available. Considered a rare disease, ATTR amyloidosis may be more prevalent than thought, particularly in older persons. Diagnosis is often delayed because of a lack of disease awareness and the heterogeneity of symptoms at presentation. Given the recent availability of effective treatments, early recognition and diagnosis are especially critical because treatment is likely more effective earlier in the disease course. The Amyloidosis Research Consortium recently convened a group of experts in ATTR amyloidosis who, through an iterative process, agreed on best practices for suspicion, diagnosis, and characterization of disease. This review describes these consensus recommendations for ATTR associated with cardiomyopathy as a resource to aid cardiologists and others in the recognition and diagnosis of ATTR associated with cardiomyopathy. Included in this review is an overview of red flag signs and symptoms and a recommended diagnostic approach, including testing for monoclonal protein, scintigraphy, or biopsy and, if ATTR associated with cardiomyopathy is identified, TTR genotyping.

AL Amyloidosis for the Cardiologist and Oncologist: Epidemiology, Diagnosis, and Management

AL amyloidosis results from clonal production of immunoglobulin light chains, most commonly arising from a clonal plasma cell disorder. Once considered a nearly uniformly fatal disease, prognosis has improved markedly over the past 15 years, predominantly because of advances in light chain suppressive therapies. Cardiac deposition of amyloid fibrils is common, and the severity of cardiac involvement remains the primary driver of prognosis. Improvements in chemotherapy/immunotherapy have prompted a reassessment of the role of advanced cardiac therapies previously considered contraindicated in most patients, including the role of implantable cardioverter-defibrillators and cardiac transplantation. This state-of-the-art review highlights the current state of the field, including diagnosis, prognosis, and hematologic- and cardiac-specific therapies.

Cardiac amyloidosis: An underdiagnosed/underappreciated disease

Cardiac amyloidosis or amyloid cardiomyopathy (ACM), commonly resulting from extracellular deposition of amyloid fibrils consisted of misfolded immunoglobulin light chain (AL) or transthyretin (TTR) protein, is an underestimated cause of heart failure and cardiac arrhythmias. Among the three types of cardiac amyloidosis (wild-type or familial TTR and light-chain), the wild-type (Wt) TTR-related amyloidosis (ATTR) is an increasingly recognized cause of heart failure with preserved ejection fraction (HFpEF), and amyloidosis should be considered in the differential diagnosis of this heart failure group of patients. Recent advances in the diagnosis and drug treatment of ACM have ushered in a new era in early disease detection and better management of these patients. Certain clues in cardiac and extracardiac manifestations of ACM may heighten clinical suspicion and guide further confirmatory testing. Newer noninvasive imaging methods (strain echocardiography, cardiac magnetic resonance and bone scintigraphy) may obviate the need for endomyocardial biopsy in ATTR patients, while newer targeted therapies may alter the adverse prognosis in these patients. Early recognition of ACM is crucial in halting the disease process before irreversible organ damage occurs. Chemotherapy and stem-cell transplantation combined with immunomodulatory therapy may also favorably affect the course and prognosis of light chain ACM. Finally, in select patients with end-stage disease, heart transplantation may render results comparable to non-ACM patients. All these issues are herein reviewed.

Prevalence of cardiac amyloidosis among adult patients referred to tertiary centres with an initial diagnosis of hypertrophic cardiomyopathy

BACKGROUND

Differential diagnosis of genetic causes of left ventricular hypertrophy (LVH) is crucial for disease-specific therapy. We aim to describe the prevalence of Cardiac Amyloidosis (CA) among patients ≥40 years with an initial diagnosis of HCM referred for second opinion to national cardiomyopathy centres.

METHODS

Consecutive patients aged ≥40 years referred with a tentative HCM diagnosis in the period 2014-2017 underwent clinical evaluation and genetic testing for HCM (including trans-thyretin-TTR). Patients with at least one red flag for CA underwent blood/urine tests, abdominal fat biopsy and/or bone-scintigraphy tracing and eventually ApoAI sequencing.

RESULTS

Out of 343 patients (age 60 ± 13 years), 251 (73%) carried a likely/pathogenic gene variant, including 12 (3.5%) in the CA-associated genes TTR (n = 11) and ApoAI (n = 1). Furthermore, 6 (2%) patients had a mutation in GLA. Among the remaining, mutation-negative patients, 26 with ≥1 CA red-flag were investigated further: 3 AL-CA and 17 wild-type-TTR-CA were identified. Ultimately, 32(9%) patients were diagnosed with CA. Prevalence of CA increased with age: 1/75 (1%) at age 40-49, 2/86 (2%) at age 50-59, 8/84 (9%) at age 60-69, 13/61 (21%) at age 70-79, 8/31 (26%) at age ≥80 (p for trend <0.01).

CONCLUSIONS

Among patients referred with and initial diagnosis of HCM, CA was the most common unrecognized mimic (9% prevalence) and increased with age (from 1% at ages 40-49 years to 26% >80 years). Age at diagnosis should be considered one of the most relevant red flags for CA in patients with HCM phenotypes; however, there is no clear age cut-off mandating scintigraphy and other second level investigations in the absence of other features suggestive of CA.

Hidden in Heart Failure

Current diagnostic strategies fail to illuminate the presence of rare disease in the heart failure population. One-third of heart failure patients are categorised as suffering an idiopathic dilated cardiomyopathy, while others are labelled only as heart failure with preserved ejection fraction. Those affected frequently suffer from delays in diagnosis, which can have a significant impact on quality of life and prognosis. Traditional rhetoric argues that delineation of this patient population is superfluous to treatment, as elucidation of aetiology will not lead to a deviation from standard management protocols. This article emphasises the importance of identifying genetic, inflammatory and infiltrative causes of heart failure to enable patients to access tailored management strategies.

Noninvasive diagnosis of hereditary transthyretin-related cardiac amyloidosis: A case report

RATIONALE

Cardiac transthyretin amyloidosis is a progressive and fatal cardiomyopathy for which several promising therapies are in development. The diagnosis is frequently delayed or missed because of the limited specificity of clinical manifestations, routine electrocardiogram, echocardiography and the traditional requirement for endomyocardial biopsy confirmation.

PATIENT CONCERNS

A 68-year-old female had suffered from lumbago for 5 years with progressive weakness, numbness in both lower limb.

DIAGNOSIS

The patient's clinical signs were not specific, but cardiac amyloidosis was suspected based on relative left ventricular apical sparing of longitudinal strain on echocardiography and continuous elevated serum levels of cardiac biomarkers (ultrasensitive cardiac troponin I and NT-proBNP). She was finally diagnosed hereditary transthyretin-related cardiac amylodosis by specific findings of cardiovascular magnetic resonance imaging (CMR), -technetium pyrophosphate (Tc-PYP) scintigraphy and genetic testing.

INTERVENTIONS

The patient received medications including diuretics, beta-blockers and angiotensin-converting enzyme inhibitors at the time of hospitalization. Ultimately, however, she refused further treatments and requested discharge from our hospital.

OUTCOMES

A series of noninvasive technique enables the diagnosis of hereditary transthyretin-related cardiac amyloidosis.

LESSONS

While endomyocardial biopsy is not able to performed, this case demonstrates that a combination of noninvasive techniques, especially CMR, nuclear imaging, and genetic testing, may help us to make a correct diagnosis of hereditary transthyretin-related cardiac amyloidosis.

Utility of 99 mTc-Pyrophosphate Scintigraphy in Diagnosing Transthyretin Cardiac Amyloidosis in Real-World Practice

Background: Amyloid transthyretin (ATTR) cardiac amyloidosis has now been recognized as one of the major causes of heart failure, especially in elderly patients. The purpose of the present study was to validate the usefulness of technetium-99 m (^{99 m}Tc)-pyrophosphate (^{99 m}Tc-PYP) scintigraphy in the screening diagnosis for ATTR amyloidosis in daily clinical practice.

Methods and Results: Ninety-eight patients underwent ^{99 m}Tc-PYP scintigraphy in the previous 3 years (PYP positive/negative, 18/80), of whom 29 underwent concomitant endomyocardial biopsy (ATTR positive/negative, 9/20). The sensitivity and specificity of ^{99 m}Tc-PYP scintigraphy for the diagnosis of biopsy-proven ATTR amyloidosis were 0.889 and 0.950, respectively. Age, gender, N-terminal prohormone of brain natriuretic peptide (NT-proBNP) level, or electrocardiogram findings did not differ significantly between PYP-positive and PYP-negative patients. Left ventricular (LV) wall thickness was significantly greater in PYP-positive than in PYP-negative patients, but LV ejection fraction or prevalence of atrial fibrillation was similar between groups. In the PYP-positive patients, higher uptake of PYP correlated with younger age and lower NT-proBNP.

Conclusions:^{99 m}Tc-PYP scintigraphy was useful, with high sensitivity and specificity in the screening diagnosis for ATTR cardiac amyloidosis, which is difficult to diagnose on clinical characteristics alone. ^{99 m}Tc-PYP scintigraphy should be considered to elucidate the underlying causes of heart failure, especially in elderly patients based on the higher prevalence of ATTR cardiac amyloidosis in this population.

Transthyretin Amyloid Cardiomyopathy: JACC State-of-the-Art Review

Transthyretin amyloid cardiomyopathy (ATTR-CM) is an under-recognized cause of heart failure (HF) in older adults, resulting from myocardial deposition of misfolded transthyretin (TTR) or pre-albumin. Characteristic patterns of echocardiography and cardiac magnetic resonance can strongly suggest the disease but are not diagnostic. The diagnosis can be made with noninvasive nuclear imaging when there is no evidence of a monoclonal protein. Amyloid fibril formation results from a destabilizing mutation in hereditary ATTR amyloidosis (hATTR) or from an aging-linked process in wild-type ATTR amyloidosis (wtATTR). Recent studies have suggested that up to 10% to 15% of older adults with HF may have unrecognized wtATTR. Associated features, including carpal tunnel syndrome and lumbar spinal stenosis, raise suspicion and may afford a means for early diagnosis. Previously treatable only by organ transplantation, pharmaceutical therapy that slows or halts ATTR-CM progression and favorably affects clinical outcomes is now available. Early recognition remains essential to afford the best treatment efficacy.

The Cardiorenal Axis: Myocardial Perfusion, Metabolism, and Innervation

PURPOSE OF THE REVIEW

Cardiorenal syndrome (CRS), defined as concomitant heart and kidney disease, has been a focus of attention for nearly a decade. As more patients survive severe acute and chronic heart and kidney diseases, CRS has emerged as an "epidemic" of modern medicine. Significant advances have been made in unraveling the complex mechanisms that underlie CRS based on classification of the condition into five pathophysiologic subtypes. In types 1 and 2, acute or chronic heart disease results in renal dysfunction, while in types 3 and 4, acute or chronic kidney diseases are the inciting factors for heart disease. Type 5 CRS is defined as concomitant heart and kidney dysfunction as part of a systemic condition such as sepsis or autoimmune disease.

RECENT FINDINGS

There are ongoing efforts to better define subtypes of CRS based on historical information, clinical manifestations, laboratory data (including biomarkers), and imaging characteristics. Systematic evaluation of CRS by advanced cardiac imaging, however, has been limited in scope and mostly focused on type 4 CRS. This is in part related to lack of clinical trials applying advanced cardiac imaging in the acute setting and exclusion of patients with significant renal disease from studies of such techniques in chronic HF. Advanced cardiac nuclear imaging is well poised for assessment of the pathophysiology of CRS by offering a myriad of molecular probes without the need for nephrotoxic contrast agents. In this review, we examine the current or potential future application of advanced cardiac imaging to evaluation of myocardial perfusion, metabolism, and innervation in patients with CRS.

Molecular Imaging of the Heart

Multimodality cardiovascular imaging is routinely used to assess cardiac function, structure, and physiological parameters to facilitate the diagnosis, characterization, and phenotyping of numerous cardiovascular diseases (CVD), as well as allows for risk stratification and guidance in medical therapy decision-making. Although useful, these imaging strategies are unable to assess the underlying cellular and molecular processes that modulate pathophysiological changes. Over the last decade, there have been great advancements in imaging instrumentation and technology that have been paralleled by breakthroughs in probe development and image analysis. These advancements have been merged with discoveries in cellular/molecular cardiovascular biology to burgeon the field of cardiovascular molecular imaging. Cardiovascular molecular imaging aims to noninvasively detect and characterize underlying disease processes to facilitate early diagnosis, improve prognostication, and guide targeted therapy across the continuum of CVD. The most-widely used approaches for preclinical and clinical molecular imaging include radiotracers that allow for high-sensitivity in vivo detection and quantification of molecular processes with single photon emission computed tomography and positron emission tomography. This review will describe multimodality molecular imaging instrumentation along with established and novel molecular imaging targets and probes. We will highlight how molecular imaging has provided valuable insights in determining the underlying fundamental biology of a wide variety of CVDs, including: myocardial infarction, cardiac arrhythmias, and nonischemic and ischemic heart failure with reduced and preserved ejection fraction. In addition, the potential of molecular imaging to assist in the characterization and risk stratification of systemic diseases, such as amyloidosis and sarcoidosis will be discussed. © 2019 American Physiological Society. Compr Physiol 9:477-533, 2019.

State-of-the-art radionuclide imaging in cardiac transthyretin amyloidosis

Cardiac amyloidosis, once considered untreatable, is now gaining well-deserved attention due to advances in imaging and the recent approval of targeted breakthrough therapies. In this paper, we discuss the role of radionuclide imaging in the evaluation and management of patients with the most common form of amyloidosis-cardiac transthyretin amyloidosis (ATTR). We provide a comprehensive summary of the literature interspersed with our institutional experience as appropriate, to deliver our perspective.

A histopathologic schema to quantify the burden of cardiac amyloidosis: Relationship with survival and echocardiographic parameters

BACKGROUND

Despite routine use of echocardiographic parameters to evaluate the severity of cardiac amyloidosis (CA), this methodology has not been well validated. We developed a histopathologic schema for quantifying CA burden and evaluated its relationship with clinical outcomes. Additionally, echocardiographic parameters were tested as potential noninvasive indices of CA burden.

METHODS

We retrospectively studied 59 patients with CA (17 light chain, 42 transthyretin) who underwent endomyocardial biopsies. Light microscopy with staining was used to categorize CA burden as mild-to-moderate (<50%) or high (≥50%). Kaplan-Meier survival analysis was performed for the two groups. In 34 patients with good-quality echocardiograms, we measured left ventricular volumes, ejection fraction (EF), interventricular septal thickness (IVSt), posterior wall thickness (PWt), LV mass, lateral e'-velocity, and global longitudinal strain (GLS). These parameters were compared between the two groups.

RESULTS

Thirty-five patients had mild-to-moderate and 24 severe amyloid burden. Kaplan-Meier curves demonstrated a trend toward worse mortality with high CA burden, which was more common and associated with higher mortality specifically in transthyretin-type patients. Echocardiography-derived IVSt, PWt, and LV mass were directly related to CA burden, while LV EF, e'-velocity, and GLS magnitude were inversely related to CA burden.

CONCLUSIONS

Our findings provided a signal that CA burden is a clinically important entity with potentially valuable prognostic information. Echocardiographic parameters of LV anatomy and function correlate with histopathologic burden of CA, which is inversely related to survival. Further studies are needed to determine whether these parameters could be used as imaging biomarkers of treatment-related changes in CA burden.

Role of cardiovascular imaging for the diagnosis and prognosis of cardiac amyloidosis

Cardiac amyloidosis (CA) describes the pathological process of amyloid protein deposition in the extracellular space of the myocardium. Unfortunately, the diagnosis of CA is often made late and when the disease process is advanced. However, advances in cardiovascular imaging have allowed for better prognostication and establishing diagnostic pathways with high sensitivity and specificity. This review discusses the role of echocardiography, cardiac MRI and nuclear cardiology in current clinical practice for diagnosis and prognosis of CA.

Tafamidis Treatment for Patients with Transthyretin Amyloid Cardiomyopathy

BACKGROUND

Transthyretin amyloid cardiomyopathy is caused by the deposition of transthyretin amyloid fibrils in the myocardium. The deposition occurs when wild-type or variant transthyretin becomes unstable and misfolds. Tafamidis binds to transthyretin, preventing tetramer dissociation and amyloidogenesis.

METHODS

In a multicenter, international, double-blind, placebo-controlled, phase 3 trial, we randomly assigned 441 patients with transthyretin amyloid cardiomyopathy in a 2:1:2 ratio to receive 80 mg of tafamidis, 20 mg of tafamidis, or placebo for 30 months. In the primary analysis, we hierarchically assessed all-cause mortality, followed by frequency of cardiovascular-related hospitalizations according to the Finkelstein-Schoenfeld method. Key secondary end points were the change from baseline to month 30 for the 6-minute walk test and the score on the Kansas City Cardiomyopathy Questionnaire-Overall Summary (KCCQ-OS), in which higher scores indicate better health status.

RESULTS

In the primary analysis, all-cause mortality and rates of cardiovascular-related hospitalizations were lower among the 264 patients who received tafamidis than among the 177 patients who received placebo (P<0.001). Tafamidis was associated with lower all-cause mortality than placebo (78 of 264 [29.5%] vs. 76 of 177 [42.9%]; hazard ratio, 0.70; 95% confidence interval [CI], 0.51 to 0.96) and a lower rate of cardiovascular-related hospitalizations, with a relative risk ratio of 0.68 (0.48 per year vs. 0.70 per year; 95% CI, 0.56 to 0.81). At month 30, tafamidis was also associated with a lower rate of decline in distance for the 6-minute walk test (P<0.001) and a lower rate of decline in KCCQ-OS score (P<0.001). The incidence and types of adverse events were similar in the two groups.

CONCLUSIONS

In patients with transthyretin amyloid cardiomyopathy, tafamidis was associated with reductions in all-cause mortality and cardiovascular-related hospitalizations and reduced the decline in functional capacity and quality of life as compared with placebo. (Funded by Pfizer; ATTR-ACT ClinicalTrials.gov number, NCT01994889 .).

Technetium pyrophosphate uptake in transthyretin cardiac amyloidosis: Associations with echocardiographic disease severity and outcomes

BACKGROUND

Quantitative uptake of Technetium 99 m-pyrophosphate (TcPYP) is sensitive and specific for diagnosing transthyretin cardiac amyloidosis (ATTR). We sought to examine the association between TcPYP uptake intensity and echocardiographic measures of disease severity and clinical outcomes.

METHODS AND RESULTS

A retrospective analysis was performed of 75 patients who underwent TcPYP scintigraphy. Planar images were evaluated semiquantitatively and using heart-to-contralateral lung (H/CL) ratio. The associations between H/CL ratio and echocardiographic parameters and outcomes were evaluated using linear regression and Cox models, respectively. There were 48 patients diagnosed with ATTR with mean H/CL ratio 1.58 ± 0.22 (vs 1.08 ± 0.09 if semiquantitative score = 0). The H/CL ratio was not associated with any measured echocardiographic parameter. Both semiquantitative uptake grade and H/CL ratio were associated with all-cause mortality (P = 0.009 and 0.007, respectively) and all-cause mortality or heart failure hospitalization (P = 0.001 and 0.020, respectively); however, neither were associated with outcomes when limited to patients with confirmed ATTR (P = 0.18 and 0.465, respectively).

CONCLUSION

In patients with suspected ATTR, quantitative and semiquantitative uptake intensity of TcPYP is associated with all-cause mortality as well as all-cause mortality or heart failure hospitalization. However, in those with confirmed ATTR, there is no association with echocardiographic disease severity or outcomes.

Prognostic utility of the Perugini grading of 99mTc-DPD scintigraphy in transthyretin (ATTR) amyloidosis and its relationship with skeletal muscle and soft tissue amyloid

Aims

High-grade (Perugini grade 2 or 3) cardiac uptake on bone scintigraphy with 99mTechnetium labelled 3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) has lately been confirmed to have high diagnostic sensitivity and specificity for cardiac transthyretin (ATTR) amyloidosis. We sought to determine whether patient stratification by Perugini grade on 99mTc-DPD scintigraphy has prognostic significance in ATTR amyloidosis.

Methods and results

Patient survival from time of 99mTc-DPD scintigraphy was determined in 602 patients with ATTR amyloidosis, including 377 with wild-type ATTR (ATTRwt) and 225 with mutant ATTR (ATTRm) amyloidosis. Patients were stratified according to Perugini grade (0-3) on 99mTc-DPD scan. The prognostic significance of additional patient and disease-related factors at baseline were determined. In the whole cohort, the finding of a Perugini grade 0 99mTc-DPD scan (n = 28) was invariably associated with absence of cardiac amyloid according to consensus criteria as well as significantly better patient survival compared to a Perugini grade 1 (n = 28), 2 (n = 436) or 3 (n = 110) 99mTc-DPD scan (P < 0.005). There were no differences in survival between patients with a grade 1, grade 2 or grade 3 99mTc-DPD scan in ATTRwt (n = 369), V122I-associated ATTRm (n = 92) or T60A-associated ATTRm (n = 59) amyloidosis. Cardiac amyloid burden, determined by equilibrium contrast cardiac magnetic resonance imaging, was similar between patients with Perugini grade 2 and Perugini grade 3 99mTc-DPD scans but skeletal muscle/soft tissue to femur ratio was substantially higher in the latter group (P < 0.001).

Conclusion

99mTc-DPD scintigraphy is exquisitely sensitive for identification of cardiac ATTR amyloid, but stratification by Perugini grade of positivity at diagnosis has no prognostic significance.

Diagnostic accuracy of bone scintigraphy in the assessment of cardiac transthyretin-related amyloidosis: a bivariate meta-analysis

PURPOSE

Cardiac transthyretin-related amyloidosis (ATTR) is a progressive and fatal cardiomyopathy. The diagnosis of this disease is frequently delayed or missed due to the limited specificity of echocardiography. An increasing amount of data in the literature demonstrate the ability of bone scintigraphy with bone-seeking radiopharmaceuticals to detect myocardial amyloid deposits, in particular in patients with ATTR. Therefore we performed a systematic review and bivariate meta-analysis of the diagnostic accuracy of bone scintigraphy in patients with suspected cardiac ATTR.

METHODS

A comprehensive computer literature search of studies published up to 30 November 2017 on the role of bone scintigraphy in patients with ATTR was performed using the following search algorithm: (a) "amyloid" OR "amyloidosis" AND (b) "TTR" OR "ATTR" OR "transthyretin" AND (c) "scintigraphy" OR "scan" OR "SPECT" OR "SPET" OR "bone" OR "skeletal" OR "skeleton" OR "PYP" OR "DPD" OR "HMDP" OR "MDP" OR "HDP". Pooled sensitivity, specificity, positive and negative likelihood ratios (LR+ and LR-) and diagnostic odds ratio (DOR) of bone scintigraphy were calculated.

RESULTS

The meta-analysis of six selected studies on bone scintigraphy in cardiac ATTR including 529 patients provided the following results: sensitivity 92.2% (95% CI 89-95%), specificity 95.4% (95% CI 77-99%), LR+ 7.02 (95% CI 3.42-14.4), LR- 0.09 (95% CI 0.06-0.14), and DOR 81.6 (95% CI 44-153). Mild heterogeneity was found among the selected studies.

CONCLUSION

Our evidence-based data demonstrate that bone scintigraphy using technetium-labelled radiotracers provides very high diagnostic accuracy in the non-invasive assessment of cardiac ATTR.

Can Nuclear Imaging Techniques Predict Patient Outcome and Guide Medical Management in Hereditary Transthyretin Cardiac Amyloidosis?

PURPOSE OF REVIEW

Nuclear imaging recently gained a key role in the diagnosis and prognostic assessment of transthyretin (TTR)-related cardiac amyloidosis. This review aims at summarizing the state-of-the art regarding the implementation of nuclear imaging in the management of hereditary mutated TTR-cardiac amyloidosis (mTTR-CA).

RECENT FINDINGS

Although cardiac uptake of bone tracers is acknowledged as a specific marker of TTR amyloid cardiac burden, recent studies validated the implementation of bone scan in the flow chart for non-invasive diagnosis and follow-up of CA in multicenter trials. Simultaneously, cardiac denervation evidenced by MIBG scintigraphy proved to be a strong and independent prognostic marker of poor outcome in mTTR-CA. By its unique ability to assess both amyloid burden and cardiac denervation, nuclear imaging may prove useful as part of multimodality imaging tools to trigger treatment initiation and monitoring in patients with mTTR-CA.

Cardiac denervation evidenced by MIBG occurs earlier than amyloid deposits detection by diphosphonate scintigraphy in TTR mutation carriers

PURPOSE

Cardiac involvement in familial transthyretin (TTR) amyloidosis is of major prognostic value, and the development of early-diagnostic tools that could trigger the use of new disease-modifying treatments is crucial. The aim of our study was to compare the respective contributions of ^99mTc-diphosphonate scintigraphy (DPD, detecting amyloid deposits) and ¹²³I-MIBG (MIBG, assessing cardiac sympathetic denervation) in patients with genetically proven TTR mutation referred for the assessment of cardiac involvement.

METHODS

We prospectively studied 75 consecutive patients (classified as symptomatic or asymptomatic carriers), using clinical evaluation, biomarkers (troponin and BNP), echocardiography, and nuclear imaging. Patients were classified as having normal heart-to-mediastinum (HMR) MIBG uptake ratio 4 h after injection (defined by HM4 ≥ 1.85) or abnormal HM4 < 1.85, and positive DPD uptake (grade ≥ 1 of Perugini classification) or negative DPD uptake.

RESULTS

Among 75 patients, 49 (65%) presented with scintigraphic sympathetic cardiac denervation and 29 (39%) with myocardial diphosphonate uptake. When MIBG was normal, DPD was negative except for two patients. Age was an independent predictor of abnormal scintigraphic result of both MIBG and DPD (HR 1.08 and 1.15 respectively), whereas echocardiographic-derived indicators of increased left ventricular filling pressure (E/e' ratio) was an independent predictor of abnormal MIBG (HR 1.33) and global longitudinal strain of positive DPD (HR 1.45). In asymptomatic patients (n = 31), MIBG was abnormal in 48% (n = 15) among whom 50% had a normal DPD; all those with a normal MIBG (n = 16) had a normal DPD.

CONCLUSIONS

In TTR mutation carriers, cardiac sympathetic denervation evidenced by decreased MIBG uptake is detected earlier than amyloid burden evidenced by DPD. These results raise the possibility of a diagnostic role for MIBG scintigraphy at an early stage of cardiac involvement in TTR-mutated carriers, in addition to its well-established prognostic value.

Wild-type transthyretin cardiac amyloidosis (ATTRwt-CA), previously known as senile cardiac amyloidosis: clinical presentation, diagnosis, management and emerging therapies

Cardiac amyloidosis is thought to be a rare group of diseases caused by extracellular deposition of misfolded proteins in the extracellular cardiac matrix resulting in heart failure with preserved ejection fraction (HFpEF). This review focuses on the similarities and differences between the pathophysiology, clinical presentation and diagnostic tests of wild-type transthyretin cardiac amyloidosis (ATTRwt-CA) compared to immunoglobulin light chain amyloidosis and hereditary cardiac amyloidosis. We address some obstacles to timely diagnosis and opportunities for management of the clinical symptoms as well as possibility of future novel disease modifying therapies.

Targeted Nuclear Imaging Probes for Cardiac Amyloidosis

PURPOSE OF REVIEW

The aim of the present manuscript is to review the latest advancements of radionuclide molecular imaging in the diagnosis and prognosis of individuals with cardiac amyloidosis.

RECENT FINDINGS

^99mTechnetium labeled bone tracer scintigraphy had been known to image cardiac amyloidosis, since the 1980s; over the past decade, bone scintigraphy has been revived specifically to diagnose transthyretin cardiac amyloidosis. ¹⁸F labeled and ¹¹C labeled amyloid binding radiotracers developed for imaging Alzheimer's disease, have been repurposed since 2013, to image light chain and transthyretin cardiac amyloidosis. ^99mTechnetium bone scintigraphy for transthyretin cardiac amyloidosis, and amyloid binding targeted PET imaging for light chain and transthyretin cardiac amyloidosis, are emerging as highly accurate methods. Targeted radionuclide imaging may soon replace endomyocardial biopsy in the evaluation of patients with suspected cardiac amyloidosis. Further research is warranted on the role of targeted imaging to quantify cardiac amyloidosis and to guide therapy.

Hip and knee arthroplasty are common among patients with transthyretin cardiac amyloidosis, occurring years before cardiac amyloid diagnosis: can we identify affected patients earlier?

Transthyretin cardiac amyloidosis (ATTR-CA) causes a restrictive cardiomyopathy in older adults, often diagnosed at advanced stages when emerging therapies in late phase clinical trials may not have clinical benefit. This investigation aimed to detect clinical entities that may provide more advanced warning of ATTR-CA. Since ATTR preferentially deposits in ligaments, tendons, and articular cartilage, we hypothesized that ATTR-CA patients have a greater prevalence of total hip (THA) and knee (TKA) arthroplasties compared with the general population, and that arthroplasty occurs significantly before ATTR-CA diagnosis. Three-hundred and thirteen patients with cardiac amyloidosis (172 with ATTR-CA, 141 with light-chain) from our institutional database were analyzed and compared to published data in over 300 million patients. Overall, 23.3% of patients with ATTR-CA and 9.2% of patients with light-chain cardiac amyloidosis (AL-CA) underwent lower extremity arthroplasty. Compared to the general population, both THA and TKA were significantly more common among patients with ATTR-CA (THA: RR 5.61, 95% CI 2.25-4.64; TKA: RR 3.32, 95% CI 2.25-4.64) but not those with AL-CA (THA: RR 1.87, 95% CI 0.85-4.08; TKA: RR 1.42, 95% CI 0.73-2.84). On an average, arthroplasty occurred 7.2 years before ATTR-CA diagnosis.

Recent advances in diagnosis and treatment of cardiac amyloidosis

Cardiac amyloidosis (CA) has been believed to be a rare disease for a long time, but recent sophisticated diagnostic modalities demonstrate that a considerable number of CA patients are hidden among those diagnosed with heart failure. Prognosis of CA was poor, but recent developments in therapeutic interventions have improved survival in these patients. Therefore, early detection and precise diagnosis is clinically important. In this review article, we overview recent progress in diagnosis and treatment for CA.

Unveiling transthyretin cardiac amyloidosis and its predictors among elderly patients with severe aortic stenosis undergoing transcatheter aortic valve replacement

AIMS

Transthyretin cardiac amyloidosis (ATTR-CA) has been reported in patients with aortic stenosis (AS) but its prevalence and phenotype are not known. We examine elderly patients with severe symptomatic AS undergoing transcatheter aortic valve replacement (TAVR) and determine the prevalence and phenotype of ATTR-CA non-invasively.

METHODS AND RESULTS

We performed technetium-99m pyrophosphate (99mTc-PYP) cardiac scintigraphy prospectively on patients who underwent TAVR, to screen for ATTR-CA. Transthoracic echocardiography and speckle-strain imaging were performed. We assessed the association of several parameters with ATTR-CA using multivariable logistic regression and constructed receiver operating curves to evaluate the best predictors of ATTR-CA. Among 151 patients (mean age 84 ± 6 years, 68% men), 16% (n = 24) screened positive for ATTR-CA with 99mTc-PYP scintigraphy. Compared with patients without ATTR-CA, ATTR-CA patients had a thicker interventricular septum (1.3 vs. 1.1 cm, P = 0.007), higher left ventricular (LV) mass index (130 vs. 98 g/m2, P = 0.002), and lower stroke volume index (30 vs. 36 mL/m2, P = 0.009). ATTR-CA patients had advanced diastolic dysfunction with higher E/A ratio (2.3 vs. 0.9, P = 0.001) and lower deceleration time (176 vs. 257 ms, P < 0.0001); impairment in systolic function with lower ejection fraction (48% vs. 56%, P = 0.011), myocardial contraction fraction (26 vs. 41, P < 0.0001), and average of lateral and septal mitral annular tissue Doppler S' (4.0 vs. 6.6 cm/s, P < 0.0001). While ATTR-CA patients had more impaired global longitudinal strain (-12 vs. -16%, P = 0.007), relative apical longitudinal strain was the same regardless of ATTR-CA diagnosis (0.98 vs. 0.98, P = 0.991). Average S' best predicted ATTR-CA in multivariable logistic regression (odds ratio 16.67 per 1 cm/s decrease with AUC 0.96, 95% confidence interval 0.90-0.99, P = 0.002) with a value ≤6 conferring 100% sensitivity for predicting a positive 99mTc-PYP amyloid scan.

CONCLUSIONS

Transthyretin cardiac amyloidosis is prevalent in 16% of patients with severe calcific AS undergoing TAVR and is associated with a severe AS phenotype of low-flow low-gradient with mildly reduced ejection fraction. Average tissue Doppler mitral annular S' of < 6 cm/s may be a sensitive measure that should prompt a confirmatory 99mTc-PYP scan and subsequent testing for ATTR-CA. Prospective assessment of outcomes after TAVR is needed in patients with and without ATTR-CA.